The present invention relates to fifth wheel couplers, and in particular, to an improved trunnion bracket and locking arrangement therefor.
Fifth wheel couplers for connecting a tractor unit to a trailer unit are known in the art, as exemplified by U.S. Pat. No. 2,985,463 to Geerds, assigned to Holland Hitch Company, the assignee of the present application, which patent is hereby incorporated by reference.
In such prior couplers, the trunnion brackets have a totally fabricated construction, and are made from a plurality of specially shaped, stamped panels of steel, which are welded together to form an assembly or weldment. This type of totally fabricated construction requires substantial manufacturing effort, time and expense. The various pieces of the assembly are first stamped out, and then bent or formed into the desired configuration. This type of fabrication process produces a high percentage of scrap and waste, which results in increased material costs. Further, the accumulation of tolerances which is experienced in this type of fabrication process can result in very difficult, time consuming assembly, and requires special welding jigs. The welding process itself creates even further inaccuracies, so that it is very difficult to maintain close tolerances.
Sliding fifth wheel couplers, incorporating a fixed base attached to the tractor and slidably mounted trunnion bracket and locking mechanism, are used to adjustably anchor the fifth wheel to permit variation in weight distribution and length. Heretofore, sliding fifth wheel couplers have used three-pronged locking plungers to connect the trunnion bracket with the slotted racks on the base plate. The three-pronged plunger design is somewhat wide, and therefore requires similarly wide windows in the sides of the trunnion bracket. Also, in prior fifth wheel assemblies, the plungers were slidingly received in inverted U-shaped channels or guides, which further increased the width of the plunger windows. As is apparent to those skilled in the art, it is advantageous to minimize the size of the plunger windows, so as to alleviate disruption of the load carrying portions of the trunnion bracket, and thereby achieve greater strength.
In the Geerds U.S. Pat. No. 2,985,463, the adjustment stops for the lock plungers are mounted on the inside wall of the trunnion bracket, and abut the interior ends of the plungers. Since the trunnion bracket can move slightly on the base plate in a lateral direction, this type of stop adjustment does not positively position the plungers with respect to the racks. Improper plunger adjustment subjects the plungers to extraordinary forces, and can cause wear. Further, the location of the adjustment stops on the interior sidewalls of the trunnion bracket makes it rather inconvenient to adjust the plungers.
Heretofore, manual release embodiments of the sliding fifth wheel arrangement, as illustrated in the Holland Hitch publication noted in the Disclosure Statement, include a pair of handles connected with the exterior ends of the plungers. This type of manual plunger operation requires that the left and right-hand plungers be independently manipulated from the opposite sides of the trunnion bracket, such that adjustment is a two man operation.